Nitro dyes, especially 2-nitroaniline derivatives, have long been used in the hair coloring art, including both oxidative and nonoxidative hair dye compositions. Such compositions typically include two or more hair dyes to provide a composite coloring effect to the hair. Depending on the shade desired, more or less of a yellow hair dye would be included. Indeed, in the dyeing of hair with a direct dye, it is necessary to provide dyes in admixture, to produce the natural shades desired.
A direct yellow dye of the prior art that is characterized by color fastness is ##STR3## which compound is described in U.S. Pat. Nos. 4,337,061 and 4,417,896. Disadvantageously, the compound (II) has less than desirable light stability.
EP No. 182,330 discloses the direct dye ##STR4## wherein R.sup.1 and R.sup.2 stand for H, C.sub.1 -C.sub.4 alkyl, C.sub.2 -C.sub.4 monohydroxyalkyl and C.sub.3 -C.sub.4 dihydroxyalkyl, except that R.sup.1 and R.sup.2 do not simultaneously stand for C.sub.1 -C.sub.4 alkyl radicals, and X is one of the radicals alkyl, monohydroxyalkyl, perfluoralkyl or halogen. Upon variation of the substituent X, the compound provides yellow shades ranging from blue-tinged lemon yellow to pure yellow to orange. Compound (III) when R.sup.1 is CH.sub.2 CH.sub.2 OH; R.sup.2 is hydrogen, and X is CF.sub.3 has a much lower affinity for hair than Compound (I) when R.sub.1 is CH.sub.2 CH.sub.2 OH, and R.sub.2 and R.sub.3 are hydrogen. Accordingly, a greater amount of the aforementioned Compound (III) is needed to obtain an equivalent color on hair.